require(HttpMethod.permitsRequestBody(method)) {
        "method $method must not have a request body."
      }
    }
    this.method = method
    this.body = body
  }

fun <T : Any> Request.Builder.commonTag(
  type: KClass<T>,
  tag: T?,
) = apply {
  if (tag == null) {
    if (tags.isNotEmpty()) {
      (tags as MutableMap).remove(type)
    }
  } else {
    val mutableTags: MutableMap<KClass<*>, Any> =

	// problems (see issues 13283 and 18518), so limit to IPv6.
	if DA.To4() == nil && DB.To4() == nil {
		commonA := commonPrefixLen(SourceDA, DA)
		commonB := commonPrefixLen(SourceDB, DB)

		if commonA > commonB {
			return preferDA
		}
		if commonA < commonB {
			return preferDB
		}
	}

	// Rule 10: Otherwise, leave the order unchanged.